A field study of ovine listerial meningo-encephalitis with particular reference to cerebrospinal fluid analysis as an aid to diagnosis and prognosis.

In a field study of listerial meningo-encephalitis involving 21 sheep from six silage-fed flocks, the neurological signs included profound depression, circling, involvement of the trigeminal and facial cranial nerves and lateral recumbency with propulsive limb movements. Within the six flocks the incidence of listerial meningo-encephalitis did not exceed 1% of the adult sheep at risk. Eleven of 18 (61%) adult animals were 2 years old. Evidence of an intrathecal inflammatory response in suspected listerial meningo-encephalitis cases was indicated by an increased cerebrospinal fluid (CSF) protein concentration greater than 0.4 g/l in 18 of 21 cases (86%), increased white cell count above 0.012 x 10(9)/l in 17 cases (81%) and lymphocyte percentage below 50% in all animals. None of the CSF parameters proved to be a reliable prognostic indicator because of the range of CSF values obtained and the small number of sheep which recovered.